The present invention involves transmitting torque to the rear wheels of a vehicle with an independent suspension. It has long been known to transmit torque from an engine transmission to a wheel through the use of joints and drive shafts. Independent suspensions require separate axles (or halfshafts) for each wheel, so that each wheel may travel independently of the other wheel. Thus, for example, if one wheel falls into a deep hole or rut, the other wheel is not lifted from the driving surface as may happen with a single axle suspension.
In driving independently suspended wheels, it has previously been considered essential to maintain the vertical alignment of the wheels of the vehicle during vertical displacement, commonly referred to as jounce and rebound. Thus, wheel joints have typically required sophisticated torque transfer mechanisms which allow a great deal (greater than 10.degree.) of angular excursion relative to the halfshaft to maintain the vertical alignment of the wheel during full jounce and rebound. This, and other variations in the physical relationship between the drive axle and the wheel have led to sophisticated joints and torque transfer mechanisms, such as constant velocity fixed joints which permit angular excursion of over 40.degree., or constant velocity plunging joints which permit angular excursion over 24.degree. and axial travel (plunging) over 50 mm, e.g. U.S. Pat. No. 4,511,346 to Hazebrook, et al.; U.S. Pat. No. 4,632,203 to Krude; U.S. Pat. No. 4,832,657 to Hahn; U.S. Pat. No. 5,167,584 to Krude; and U.S. Pat. No. 5,290,203 to Krude, which are incorporated by reference herein.
With respect to propeller shafts, it has also been known to utilize a rounded spline within a splined sleeve as a joint to transfer torque between aligned shafts where minimal angular excursion or axial travel is generated, such as U.S. Pat. No. 4,824,418 to Taubert, and U.S. Pat. No. 4,913,681 to Green. While these joints are inexpensive to make, their use is heretofore restricted to drive shafts where the components are fixed and aligned, rather than for use in halfshaft assemblies. An example of such a use is in the Honda ATV (Four Trax), which provides a single swing suspension for both rear wheels, and utilizes a crown spline joint on the rear propeller shaft.
Further, Cardan joints, also referred to as Hooke's universal joints, have long been known to provide for the transfer of torque between axles while permitting an angle between shafts of up to 30.degree.. Such joints have typically only been used in connection with axially fixed components or in conjunction with plunging joints which compensate for axial travel, as the interconnecting pin arrangement of a Cardan joint is susceptible to fatigue from axial loading (See e.g. U.S. Pat. Nos. 4,669,571 and 4,819,756, incorporated by reference herein). These patents detail the limitations of the Cardan joint and illustrate the use of constant velocity universal joints with a hinge type independent suspension.
In spite of these varied and sophisticated drive systems and joints, there is no known assembly which permits the use of a crowned spline joint at the wheel and a Cardan joint at the transmission output in a halfshaft assembly for an independently suspended wheel.